Electromechanical actuators are rapidly displacing hydraulic devices in a wide range of industries, including aviation. Improvements in solid state switching devices, their digital control and in the performance of magnetic materials have all contributed to an increased interest in electric actuators. Electromechanical linear actuators are particularly well suited to flight control applications, as well as a multitude of industrial uses, particularly in production automation. Automotive and other vehicle applications also abound, as may be found, for example, in the variable transmissions and caliper or disk brake actuators described in, e.g., U.S. Pat. Nos. 6,837,818 and 6,626,778 to Kapaan et al., and U.S. Pat. Nos. 6,367,597 and 6,318,512 to De Vries et al.
Flight applications, such as actuation of control surfaces, helicopter rotor blades, lift enhancement devices, landing gear deployment and braking, door opening, and the like, are all best handled with linear actuators. Rotary-to-linear conversions, correctly engineered, can provide backlash-free operation, high stiffness, high slew rates, good overall efficiency and high frequency response, which properties are all needed in combination for an ideal flight control actuator.
Concomitant with their widespread adoption, certain shortcomings in various mechanical aspects of the devices have also become apparent, and therefore merit attention. These problems include backlash, wear, complexity and cost and life limitations.
Accordingly, there is a long-felt but as yet unsatisfied need in a number of fields for linear actuators that overcome the backlash, rapid wear, complexity, high cost and limited life problems incident to prior art actuators, and that provide backlash-free operation, higher stiffnesses, slew rates and frequency responses, and better overall efficiency.